Hey Daniel!

Sounds pretty benign. If you have no pain with movement or instability and it’s not affecting your activity I would just monitor it and let it heal. I wouldn’t directly or aggressively do soft tissue work on that exact spot till it goes away but otherwise would carry on as normal. If you notice this starts happening regularly and are frequently getting these unexplained bruises I would go get it checked out just to make sure it’s not due to some other underlying issue or if you happen to be taking any medications that are associated with increased bleeding or bruising.

-Mike